Airbag covering cap comprising a support layer and a cover layer of different elasticities

ABSTRACT

The invention relates to an airbag covering cap comprising a support layer and a covering layer of different elasticities, having at least one tear-off line along which the airbag covering cap tears open when the airbag is deployed. The covering layer is weakened by a groove in the region of the tear-off line and the support layer extends into this groove. In accordance with the invention, the covering layer ( 13 ) has a section ( 13   a ), adjacent to the section ( 11   a ) of the support layer ( 11 ), which extends into said support layer ( 11 ). The edge between the sections ( 11   a,    13   a ) of the support and covering layers ( 11, 13 ), each extending into the other layer, is configured as a tear-off edge ( 14, 15 ).

[0001] The invention relates to an airbag covering cap comprising a support layer and cover layer of different elasticities according to the preamble of claim 1.

[0002] From DE 195 16 230 an airbag cover is known which consists of a moulded part as the support layer and a visible covering which covers the moulded part to form the cover layer. The cover layer is formed as a leather coating with a groove-like partial reduction in the material thickness into which the support layer is stretched. At this point an ideal break point is formed in the support layer and the path of the break point corresponds to that of the groove of the cover layer, i.e. the ideal break points in the support and cover layer overlap one another.

[0003] Through rear injection of the cover layer, moulded into the groove, it happens that there is no material reduction which can be seen on the visible side of the sight cover and a smooth surface is produced on the visible side of the cover layer. Ornamental grooves, such as are provided in the event of weakening the upper side of the cover layer are therefore not required.

[0004] With this covering, as with other known coverings having weakened lines it is intended that the cover tears open along the weakened lines in the event of a crash. Tearing open should however not continue over the end of the weakened lines. The drawback with the known covering described above is however that further tearing beyond the end of the groove cannot be ruled out.

[0005] In order to prevent further tearing it is known to provide a small opening at the end of the groove whereby the opening has a larger diameter than the width of the break line. This however has the drawback that the surface of the cover is broken so that the appearance is impaired.

[0006] Furthermore it is known from DE 44 24 6586 A1 to design the end sections of the break line curved so that further tearing beyond the end of the break line is likewise to be prevented.

[0007] All the known covering caps have the drawback that the opening and tearing force cannot be changed without changing the optical and/or mechanical properties of the covering cap. If the groove is indented for example to reduce the tear-open force then at the same time the risk of further tearing at the ends is increased.

[0008] The object of the invention is to allow, in the case of an airbag covering cap having a smooth cover surface layer, the cap to tear open at a lower force without the cap continuing to tear further over the end of the proposed break line, and to change the opening and further tearing force without changing the optical and/or mechanical properties.

[0009] This is achieved according the invention according to the features of the claim 1.

[0010] In the case of an airbag covering cap comprising a support and a cover layer of different elasticity with at least a tear-off line along which the airbag covering cap tears open as the airbag is deployed, wherein the cover layer is weakened in the area of the tear-off line through a groove and the support layer extends into this groove, according to the invention the cover layer has adjoining the section of the support layer which extends into the groove a section which extends into the support layer whereby the edge between the sections of the cover layer and support layer which each extend into each other layer, is formed as the tear-off edge.

[0011] As opposed to the known airbag covers both the support layer and the cover layer have a reinforced section in the area of the break point. Between these two sections stretches a tear-off edge running through both layers, i.e. this tear-off edge is, seen in cross-section, substantially longer than with the known covering caps. The covering cap in the event of a crash tears open along this tear-off edge starting from the weakened lines above the groove in the cover layer whereby the adhesion between the material of the support and the cover layer is slight along the tear-off edge. The reinforced sections and the extended tear-off edge on the one hand prevent the airbag covering cap from tearing open further at the end of the groove of the cover layer and on the other hand ensures in addition that the airbag covering cap tears open along the proposed line.

[0012] In one embodiment the support layer is designed weaker in the area of the tear-off edge between the sections of the support and covering layers compared to the remaining areas and the cover layer extends into the weakened area. With this embodiment both the cover layer and the support layer are formed continuous in the area of the tear-off edge. The airbag cover tears open in the event of a crash both at the weakened points of the cover layer and of the support layer and along the tear-off edge between the two.

[0013] In a further embodiment it is proposed that the support layer has in the area of the tear-off edge between the sections of the support and cover layers at least one slit and that the cover layer extends at least partially into the slit. With this embodiment the support layer is formed non-continuous in the area of the tear-off edge. Thus with this embodiment in the event of a crash the airbag cover must only tear in at the weakened point of the cover layer. It then tears open again along the tear-off edge between the support and cover layer.

[0014] In a third embodiment a slit is likewise provided which is however bridged by thin narrow webs. The webs preferably have a width of 0.8 mm maximum and are arranged at intervals of at least 10 mm.

[0015] The thickness of the cover layer above the section of the support layer extending into the cover layer preferably increases towards the ends of the tear-off areas whereby further tearing of the cover cap can be affected.

[0016] In a further design of the second embodiment it is proposed that the edge of the slit in the support layer is reinforced like a bead. A reinforcement of this kind is likewise possible with the first embodiment at the edges of the weakened area in the support layer. It is thereby further ensured that the airbag cover does not tear open apart from the proposed tear-open areas.

[0017] It is expedient if the tear-off edge runs inclined relative to the surface of the cover layer and the support layer in this area. By changing the inclined path and the path of the tear-off edge in cross-section it is possible to adjust the initial tearing and further tearing forces without changing the optical or mechanical properties. The tear-off edge preferably runs straight in cross-section but can also run angled in a straight line or curved.

[0018] The reduced adhesion provided between the support and cover layer at the tear-off edge can be achieved by selecting suitable materials for the support and cover layer whereby then the adhesion is also reduced in the remaining areas. The reduced adhesion can however also be achieved by surface treating the support layer in this area prior to applying the cover layer.

[0019] It is expedient to use thermoplastics elastomers as the support layer and cover layer.

[0020] The invention will now be explained with reference to the embodiments shown in the drawings in which:

[0021]FIG. 1 is a view of the underneath of a covering cap;

[0022]FIG. 2 is a sectional view through the covering cap according to FIG. 1;

[0023] FIGS. 3 to 6 show different embodiments of the tear-off area of the covering cap in an enlarged view of the detail marked by a circle in FIG. 2;

[0024]FIG. 7 shows a view from below of the detail of FIG. 6 with a continuous web;

[0025]FIG. 8 shows a view from below of the detail of FIG. 6 with several narrow webs.

[0026] The covering cap 1 shown in FIG. 1 is to tear open into two parts in the event of a crash. To this end two folding areas 2, 3 are provided which have in the centre of the covering cap a common tear-off area 4. At the ends there are separate tear-off areas 5, 6 and 7, 8 which open into hinge-like sections 9, 10 which are designed in known way for example as film hinges and are not shown in detail.

[0027] It can be seen from FIG. 2 that the covering cap has a support layer 11 with an edge 12 and that a cover layer 13 is provided over the support layer 11. Both preferably consist of plastics whereby the material of the cover layer is softer than the material of the support layer. The cover layer 13 has a continuous surface whilst it is designed on the underneath in the manner according to the invention.

[0028] In a first embodiment which is shown on an enlarged scale in FIG. 3, the cover layer has in the tear-off area 4-8 a groove into which a section 11 a of the support layer extends. The support layer has in the tear-off area 4-8 a slit i.e. the folding areas 2, 3 are separated from each other in the support layer. A section 13 a of the cover layer 13 extends into this slit. A tear-off edge 14 runs between the two sections 11 a and 13 a. In the present embodiment this tear-off edge runs in a straight line in cross-section and extends practically through the entire support and cover layers. The support and cover layers receive increased strength in the area of this tear-off edge 14 through the reinforced sections 11 a and 13 a so that further tearing at the ends of the tear-off areas 5-8 which adjoin the hinge-like sections 9, 10 is prevented. Furthermore by changing the incline of the tear-off edge 14 it is possible to affect the force required for initially tearing and further tearing the cover cap without changing the optical and mechanical properties of the tear-off area, i.e. both the continuous surface of the cover layer 13 and also the reinforced sections 11 a and 13 a remain.

[0029] The thickness d of the cover layer 13 above the section 11 a preferably amounts to a few tenths millimetres and at the ends of the tear-off areas 5-8 to about one millimetre.

[0030] During inflation the support layer 11 and the cover layer 13 expand differently as a result of unequal elasticity. The cover material tears in over the reinforced section 11 a of the support layer 11 and becomes detached from the support material along the inclined tear-off edge 14. The adhesion between the support and cover layers is however on the other side so great that the two remain joined together during tearing of the covering cap in the remaining areas so that the covering cap tears open completely.

[0031] With the embodiment of FIG. 4 there is a different path for the tear-off edge compared with the embodiment of FIG. 3. In cross-section this tear-off edge 15 runs straight with angles, i.e. it has two sections which run at different angles relative to the surface of the covering cap.

[0032] A modification of the embodiment of FIG. 4 is shown in FIG. 5. There the support layer has in the area of the tear-off edge 15 bead-like reinforcements 16, 17.

[0033] The process of the further tearing along the tear-off edge 15 is thereby further improved.

[0034] In FIG. 6 the two embodiments of FIGS. 7 and 8 are shown in cross-section which is the same in both cases. With the embodiment of FIG. 7 the support layer 11 has no slit in the area of the tear-off edge but a weakening in the material so that a web 18 remains. In the present embodiment the weakening has been provided on both sides. The weakened section 13 a of the cover layer 13 extends into the weakened area of the support layer up to the web 18. The web has such a width that despite the different elasticities of the support and cover layer it tears open together with the cover layer above the reinforced section 11 a.

[0035] In the embodiment of FIG. 8 the support layer 11 has a slit which is bridged by webs 19 which extend from one side of the support layer 11 to the other side. The reinforced section 13 a can thus be seen in FIG. 8 between the webs 19. 

1. Airbag covering cap consisting of a support and cover layer of different elasticity with at least one tear-off line along which the airbag covering cap tears open in the event of an unfolding airbag whereby the cover layer is weakened in the area of the tear-off line by a groove and the support layer extends into this groove, characterised in that the cover layer (13) has adjoining the section (11 a) of the support layer (11) which extends into the groove a section (13 a) which extends into the support layer (11) whereby the edge between the sections (11 a, 13 a) of the support and cover layer (11, 13) which each extend into each other layer, is formed as a tear-off edge (14, 15).
 2. Airbag covering cap according to claim 1 characterised in that the support layer (11) is formed weaker in the area of the tear-off edge (14) than in the remaining areas and that the cover layer (13) extends into the weakened area.
 3. Airbag covering cap according to claim 1 or 2 characterised in that the support layer (11) has in the area of the tear-off edge (14, 15) at least one slit and that the cover layer (13) extends at least in part into the slit.
 4. Airbag covering cap according to claim 3 characterised in that the slit is bridged by thin narrow webs (19).
 5. Airbag covering cap according to claim 3 or 4 characterised in that the webs (19) have a width of 0.8 mm maximum and are arranged at intervals of at least 10 mm.
 6. Airbag covering cap according to at least one of the preceding claims characterised in that the thickness (d) of the cover layer (13) above the section (11 a) of the support layer (11) extending into the cover layer increases to the ends of the tear-off areas (5-8).
 7. Airbag covering cap according to at least one of claims 3 to 6 characterised in that bead-like reinforcements (16, 17) are provided on the edge of the slit.
 8. Airbag covering cap according to at least one of the preceding claims characterised in that the tear-off edge (14, 15) opposite the surface of the cover layer and support layer runs inclined in this area.
 9. Airbag covering cap according to at least one of the preceding claims characterised in that the tear-off edge (14, 15) in cross-section runs in a straight line, angled in straight lines or curved.
 10. Airbag covering cap according to at least one of the preceding claims characterised in that the support and cover layers (11, 13) have reduced adhesion at the tear-off edges (14, 15).
 11. Airbag covering cap according to at least one of the preceding claims characterised in that a material is used for the support and cover layers (11, 13) wherein the mutual adhesion is reduced.
 12. Airbag covering cap according to at least one of the preceding claims characterised in that the support and cover layer (11, 13) consist of thermoplastics elastomers. 